1. Field of the Invention
The present invention relates to a motor and, more particularly, to a motor having a balancing plate. The present invention also relates to a heat dissipating fan including such a motor.
2. Description of the Related Art
Conventional heat dissipating fans generally include a motor driving an impeller to rotate for heat dissipating purposes. A typical motor includes a base or a substrate, a stator, and a rotor. The base supports the stator and the rotor. The stator is coupled to the base, and the rotor is rotatably coupled to the stator and can be driven to rotate by the stator. In order to provide stable rotation of the rotor, it is usual to mount a balancing magnet, a balancing ring, a balancing plate, or the like to the base or substrate.
FIG. 1 shows a conventional motor 5 including a base 51 on which a shaft tube 52 is formed and located in a center of a stator 56. A rotor 53 includes a hub 531 and a shaft 532 extending from the hub 531 and rotatably received in the shaft tube 52. A balancing magnet 54 is mounted in a top end of the shaft tube 52. A magnetically conductive portion 55 is mounted to the hub 531 and aligned with the balancing magnet 54. Stable rotation of the rotor 53 and stable starting can be obtained by the balancing magnet 54 that magnetically attracts the magnetically conductive portion 55. An example of such a motor 5 is disclosed in Taiwan Patent No. I2564440. However, mounting of the balancing magnet 54 in the top end of the shaft tube 52 and mounting of the magnetically conductive portion 55 to the hub 531 are troublesome and result in an increase in the number of the elements and hence, the costs of the motor 5. Furthermore, a spacing is required between the magnetically conductive portion 55 and the balancing magnet 54 such that the overall axial length of the motor 5 can not be effectively reduced.
FIG. 2 shows another conventional motor 6 including a stator 61, a balancing magnet 62, a rotor 63, and a metal casing 64. The balancing magnet 62 is mounted to the stator 61. The rotor 63 includes a permanent magnet 631 aligned with the stator 61. The metal casing 64 is mounted to an inner side of the rotor 63. The balancing magnet 62 and the metal casing 64 provide a magnetic balancing force therebetween to maintain stable rotation of the rotor 63. An example of such a motor 6 is disclosed in Taiwan Patent Publication No. 590330. However, mounting of the metal casing 64 in the rotor 63 is difficult. Furthermore, the balancing magnet 62 has to be mounted to the stator 61. Thus, the assembly of the motor 6 is not easy while having the disadvantages of many elements and high manufacturing costs. Further, a spacing is required between the rotor 63 and the stator 61 for receiving the metal casing 64 and the balancing magnet 62. As a result, the overall axial length of the motor 6 can not be effectively reduced.
FIG. 3 shows a further conventional motor 7 including a base 71, a first balancing magnet 72, a rotor 73, and a second balancing magnet 74. The base 71 supports a stator 711 to which the rotor 73 is rotatably coupled. The first balancing magnet 72 is coupled to the base 71. The second balancing magnet 74 is coupled to the rotor 73 and aligned with the first balancing magnet 72. The first and second balancing magnets 72 and 74 are spaced in an axial direction and attract each other to maintain rotational balance of the rotor 73. An example of such a motor 7 is disclosed in Taiwan Patent No. 1257757. However, mounting of the first and second balancing magnets 72 and 74 on the base 71 and the rotor 73, respectively, is troublesome while having a complicated structure and high manufacturing costs. Furthermore, the second balancing magnet 74 is liable to disengage from the rotor 73 when the rotor 73 rotates for a long period of time. Further, the first balancing magnet 72 on the base 71 inhibits reduction in the overall axial length of the motor 7.
FIG. 4 shows still another conventional motor 8 including a substrate 81, a stator 82 coupled to the substrate 81, and a rotor 83 rotatably coupled to the stator 82. The rotor 83 includes a permanent magnet 831. A balancing ring 84 is coupled to the substrate 81 and includes an annular wall 841. The annular wall 841 of the balancing ring 84 and a bottom section of the permanent magnet 831 attract each other to maintain rotational balance of the rotor 83. An example of such a motor 8 is disclosed in Taiwan Patent Publication No. 501823. However, the balancing ring 84 having the upright annular wall 841 renders a complicated structure that can not be formed easily and increases the overall axial length of the motor 8. Furthermore, mounting of the balancing ring 84 to the substrate 81 is not easy.
Conclusively, the above-mentioned motors 5, 6, 7, and 8 suffer from the disadvantages of complicated structure, inconvenient assembly, difficulties in reduction of the overall axial length, and high manufacturing costs. Other conventional structures, such as those disclosed in Taiwan Patent Publication No. 200638658, Taiwan Patent No. I246817, and Taiwan Utility Model No. M243848, also suffer from the same disadvantages. Taiwan Patent Publication No. 421369 discloses a brushless DC motor including a rotor and a stator having a plurality of magnetic pole plates, and one of which provides the balancing function for the rotor. However, manufacture and assembly of the stator are very difficult.